Typical gas turbine engine fuel supply systems include a fuel source, such as a fuel tank, and one or more pumps. The one or more pumps draw fuel from the fuel tank and deliver pressurized fuel to one or more primary fuel loads and to one or more secondary fuel loads via one or more supply lines. Generally, the primary fuel loads, which include the fuel manifolds in the engine combustor, are supplied with fuel via, for example, a priority flow line. The secondary fuel loads, which may include a motive flow valve and regulator, one or more variable geometry actuators, and one or more bleed valves, are supplied with fuel via, for example, a secondary flow line.
Recently, there has been a desire to implement fuel supply systems with electric pumps. In such systems, fuel flow is controlled by, for example, controlling the speed of the electric pump, rather than the position of a metering valve and/or a bypass flow valve. Preferably, the electric pump is sized to supply the maximum fuel flow that may be needed by allow of the system loads. Thus, for systems that include one or more secondary fuel loads, the electric pump may need to be sized to supply a higher flow rate than what is needed by just the primary fuel loads. As a result, the overall fuel system design may exhibit certain undesirable drawbacks. For example, a relatively larger electric pump may generate excessive fuel system heat, and/or may increase overall fuel system weight and costs.
Hence, there is a need for a fuel supply system that uses an electric pump to control fuel flow to one or more primary loads and that is able to supply fuel to secondary fuel loads without generating excessive fuel system heat, and/or increasing overall fuel system weight and/or costs. The present invention addresses one or more of these needs.